I watched the new blu ray release with the correct mono the other night, and I could hear faint background noise throughout. It's certainly better than the lossy mono on the 2007 disc.
One little detail about the tv footage I had forgotten about is that there was a title card with a date before the auditorium scene with Loomis that's gone missing. Did any of the previous releases have that? I can't dig out my Criterion to check at the moment.